#!/usr/bin/env python3 # -*- coding: utf-8 -*- class switch(object): """ This class provides the functionality we want. You only need to look at this if you want to know how this works. It only needs to be defined once, no need to muck around with its internals. """ def __init__(self, value): self.value = value self.fall = False def __iter__(self): """Return the match method once, then stop""" yield self.match raise StopIteration def match(self, *args): """Indicate whether or not to enter a case suite""" if self.fall or not args: return True elif self.value in args: self.fall = True return True else: return False # The following example is pretty much the exact use-case of a dictionary, # but is included for its simplicity. Note that you can include statements # in each suite. """ v = 'ten' for case in switch(v): if case('one'): print(1) break if case('two'): print(2) break if case('ten'): print(10) break if case('eleven'): print(11) break if case(): # default, could also just omit condition or 'if True' print("something else!") # No need to break here, it'll stop anyway """ # break is used here to look as much like the real thing as possible, but # elif is generally just as good and more concise. # Empty suites are considered syntax errors, so intentional fall-throughs # should contain 'pass' """ c = 'z' for case in switch(c): if case('a'): pass # only necessary if the rest of the suite is empty if case('b'): pass # ... if case('y'): pass if case('z'): print("c is lowercase!") break if case('A'): pass # ... if case('Z'): print("c is uppercase!") break if case(): # default print("I dunno what c was!") """ # As suggested by Pierre Quentel, you can even expand upon the # functionality of the classic 'case' statement by matching multiple # cases in a single shot. This greatly benefits operations such as the # uppercase/lowercase example above: """ import string c = 'A' for case in switch(c): if case(*string.lowercase): # note the * for unpacking as arguments print "c is lowercase!" break if case(*string.uppercase): print("c is uppercase!") break if case('!', '?', '.'): # normal argument passing style also applies print("c is a sentence terminator!") break if case(): # default print("I dunno what c was!") """ # Since Pierre's suggestion is backward-compatible with the original recipe, # I have made the necessary modification to allow for the above usage.